So we finally tracked down the oil leak (oil pump o-ring) in our '94 Celica GT that we are building for the Lemons series and now we have a new problem. The oil light is coming on at idle.

Quick background:
In tracking down the oil leak we have changed the camshaft seal, oil pump seal and oil pump o-ring. Upon removing the cam cover (to replace the gasket) we could see a large gunk buildup in the head (old oil). After fiixng the oil leak we ran engine gunk cleaner through the motor and drained the oil. Before refilling we dropped the pan (to clean out excess gunk) and found the oil pickup to be almost clogged. We cleaned it out very well and reinstalled everything, filled with 10W-40 and she fired right up. Drove around the block and she feels fine and sounds fine but the oil light is flickering on at idle sometimes.

During the cleanout we cut open the old filter and found some bits of metal but only very small dots. Not sure how old that filter was either. Car has 164,000 miles and sat for a year or so before we got her. PO parked her because of the chronic oil leaking.

We're hoping that the oil pressure sending unit could be gunked up as well and not reading correctly at low pressure. More like crossing our fingers...

Questions:
We want to add an oil pressure gauge (instead of idiot light). Has anyone done this on this motor. I have read there is a thread issue on this port. True?

Other than the possibility of the sending unit being clogged or the bearings being wiped out or the oil pump being bad, any other thoughts on what might be causing this that we should check?

That O ring almost cost me a motor. I caught it just in time. It cost someone else here a motor.

I dunno about any thread issues. I'm not sure what a 5SFE has for oil sender threads, but on a 4AG block, the threads are BSPT (British Standard Pipe Tapered). The S blocks are of about the same era as the A blocks, so I wouldn't be surprised if they have BSPT threads as well.

Dr. Hess wrote:
That O ring almost cost me a motor. I caught it just in time. It cost someone else here a motor.

Do you mean the oil pump o-ring? It was hard as a rock and just gushing oil.

Is there such a thing as a BSPT oil pressure sending unit or will I have to get an adaptor?

Great (relatively) to hear about the electrical issues. We will track down the leads and see if anything looks bad enough to be causing the issue. I will be much happier if we can get an oil pressure gauge in it though.

Yeah, the oil pump O ring. It had been leaking. Real hard to find the leak, as you mention. Finally, the blew out and went through 4 quarts of oil in 20 miles. Took me 2 gallons to get home.

AE92's have a BSPT oil pressure sender. Actually, just go to the junk yard and walk around the Toyota section and try to find a 5S motor with a oil pressure guage instead of an idiot light. Take the sender off that. Next best would be to look for a Corolla with a pressure guage. The AE92's all have one, 4AF, 4AFE and 4AGE. It's probably the same as the S block. Bring your idiot light sender to compare. If I remember, you need a really thin open ended wrench to get the senders off. Maybe one somewhat pretzel shaped. I think I had to make one.

I'm sure you could get something from Pegasus, etiher an adapter or a sender. I don't remember if it is 1/8" BSPT or 1/4". I think it's 1/8", but check that yourself.

An update: We pulled the oil pressure sensor last night and it looked gunky so we cleaned it well and reinstalled. The plug to the sensor was basically falling apart so we crimped the female lead a little and jammed it onto the sensor. So good so far. We had a lot of fittings that seemed to match the sensor thread pattern but would not thread into the block more than 1-2 turns so no luck on installing a true pressure gauge yet. Hopefully we can hit the JY this weekend and find the correct sender unit.

An update. Finally got a BSP/NPT adaptor and got a mechanical gauge on the engine. Starts up fine with 25 psi and holds at 50 psi when revved. However, after warming up a few minutes the pressure drops to 0 and will not budge regardless of rev level. My guess (hope) is that the relief valve on the oil pump is sticking open causing the majority of the flow to bypass to the pan, hence the pressure drop.

Ok, so we tried it again last night and now there is no drop in oil pressure. We ran the car, got it up to operating temp and let it idle. Sat at a solid 25 psi. We swapped the gauge for another one and tried again with the same results... Very strange. I'm going to drive it around some after work to see what she does. The oil pressure gauge is securely duct taped to the hood for easy viewing...

With all that gunk a sticky relief valve is a possibility.
It sounds as if that may have happened. Then it became unstuck. Keep an eye on the gauge.
On our race car, we had a sender that turned on a big yellow light if the pressure dropped below 20 psi.

Hi Guys,
I have a 94 Gt that has just developed the "mistery oil leak", it has 150,000 miles and just started to drip pretty steady the last week or so, half a quart per 100 miles would be my guess. I steamed the engine and parked it, waiting for above freezing temps to proceed. The oil appears to be coming from the back of the engine and the main flow of dripping comes down off the oil pan near the drain plug. Any other hints would be appreciated.
What is the general proceedure to get to that oil pump "O" ring? Does the engine have to be loosened and lifted etc?... Thanks.
Vance in Denver

There is a little gasket between the pickup tube and the pump, that will cause issues if it's leaking or missing. if the oil splash tray is installed incorrectly, that will cause issues. The oil pressure switch in the S series engines is 1/8 BSPT. It is the lowest pressure point, also. I think it is set to go off around 15-20 psi.

Check that your PCV system is working, to make sure you're not pushing oil. The distributor o-rings also like to leak, and the oil travels surprisingly far.

If you have to break the crank pulley bolt loose, try putting a breaker bar and cheater pipe on it, with the handle pointing toward the front of the car and against the ground, then bump the starter. Might work, probably won't.

I'm putting my money on the oil pump O ring. Pukes out from the front of the motor (harmonic balancer front, not car front). My 97 Camry was doing that. It wasn't that bad and I didn't worry too much about it. Then, I drove it to work one day (fortunately, because Dr.Linda usually drove it) and 1 block from work, the oil light came on. I killed the motor and coasted to the parking lot. Oil was MT. 2 gallons got me home 40 miles. I had to stop and add the 2nd gallon half way.

So, what you need to do is do a timing belt job. When you are that far down into it, it's only an extra 10 minutes to pull the pump off and put a new O ring on. Get an O ring from the dealer. It's like 5 bucks or something. I'm sure there's plenty of w3bz showing a 5sfe timing belt, or get a Chiltons or Haynes as they go over it pretty well.

Thanks Dr.
I was thinking timing belt water pump combo plate, at 150,000 miles makes sense anyway .... I'll do the oil pump "o" ring as long as I'm in there. ( hopefully my brother in law will be in there! He is a certified Honda tech with many years of service )...
Going to try Tylers idea first.

DR,
I have the chilton book, have no looked yet ... How much labor time would a good tech need to do the Oil pump "O" ring?
I stopped driving the car by the time it lost the first quart or less, so caught it pretty quick, parking spot was wet.

As I said above, if you have it down for a timing belt, it is probably an additional 10 minutes. A professional mechanic should be able to do that in 5 minutes extra. Really. It is nothing. Like 6-8 bolts, pull the pump off, put the new O ring on, put the pump on, put the bolts back in. I, personally, feel that every timing belt change should include that O ring, after what I went through. At least every other timing belt change. You are changing them at the 60K mile spec, right?